This invention relates generally to a latch mechanism and, in particular, to a latch mechanism that is suitable for edgemounting. While a variety of edgemount latch mechanisms are known in the art, these mechanisms have generally been less than completely satisfactory with regard to tamper-resistance. Heretofore, locking mechanisms locked only one of the linkages within the latch mechanism thereby allowing the locking mechanism to be bypassed. Furthermore, latch mechanisms have not provided a sufficient force to maintain the door against the gasket and door frame when the latch mechanism is in a latched position. The instant invention provides a construction directed to overcoming the aforenoted disadvantages.